1. Field of the Invention
This invention relates to an improvement in the demetallization of petroleum feedstocks. In particular, it relates to the removal of arsenic from shale oil and other mineral oils.
2. Prior Related Art
In the refining of crude oils, difficulties are encountered when hydrocarbon crudes, such as crude shale oils, which contain more than about 2 ppmw arsenic, must be processed. Arsenic present in such concentrations, particularly when it exceeds 5 or 6 ppmw, quickly deactivates hydrocracking, hydrotreating, and other refining catalysts. Hence, to avoid the premature replacement of expensive catalysts, it is necessary to remove the arsenic from shale oils and the like prior to conventional refining.
One method known for removing arsenic from shale oil is disclosed in U.S. Pat. No. 3,804,750 to Myers et al. It is shown therein that a hydrotreating catalyst comprising nickel sulfide, molybdenum sulfide, and alumina is useful for removing an amount of arsenic equal to no more than about 7.7% of the weight of the catalyst. (By way of comparison, the catalytic absorbents utilized in the process described herein are useful for removing an amount of arsenic at least equal to 23.6% of the weight of said catalytic absorbents.) Another method is shown in U.S. Pat. No. 3,876,533 to Myers. It is disclosed therein that particles comprising oxides and/or sulfides of iron, cobalt, and nickel can be used to adsorb arsenic. As the arsenic is adsorbed, portions of the particles containing the deposited arsenic flake off and are subsequently collected by filtration.
The difficulties with the prior art processes reside in the fact that one is left with a choice of either using a low capacity but costly adsorbent or installing expensive filtration equipment. Accordingly, it is an object of this invention to reduce the concentration of arsenic in shale oil by contacting the shale oil with a high capacity, cohesive catalytic absorbent. Other objectives and advantages will appear to those skilled in the art from the specification including claims herein.